Plasma spraying is a process in which a coating material is sprayed by a plasma spray device onto a target surface to provide a desired coating. In a conventional plasma spray device, the induced swirling of gas around the cathode centrifugally ejects any injected coating material away from the plasma stream after it exits the anode, reducing the amount of coating material applied to the target surface. In some plasma spray devices, the plasma stream exiting the anode may have an overall particle pattern angle of greater than 90°. The resulting depositional efficiency of the spraying process may be as low as 25% in such an arrangement. Such a low depositional efficiency results in increased costs arising from longer processing times and wasted coating materials.
Moreover, a conventional plasma spray device may experience high consumable wear, requiring the frequent replacement of parts worn down by constant contact with the high energy DC arc which ignites the plasma.
What is needed is a plasma spraying process and apparatus with an increased depositional efficiency and a longer consumable life. The present invention satisfies these needs and provides other advantages as well.